
The quake struck 39 kilometres (24 miles) northwest of the city of Kangding in the mountainous west of the province at 4:55 pm (0855 GMT) at a depth of nine kilometres, the USGS said.
There were no immediate reports of casualties or damage.
China Earthquake Networks Center measured the quake at 6.3, according to the state-run Xinhua news agency.
China is prone to deadly earthquakes.
In May 2008, a 7.9 magnitude quake rocked Sichuan, killing more than 80,000 people and flattening swathes of the province.